1. Field of the Invention
The present invention relates in general to a small watercraft, and in particular to a hull construction for a small watercraft.
2. Description of Related Art
Personal watercrafts have become popular in recent years. This type of watercraft is sporting in nature; it turns swiftly, is easily maneuverable, and accelerates quickly. Personal watercraft today commonly carrier one rider and possibly one or two passengers.
A relatively light weight, small hull of the personal watercraft defines an engine compartment below a rider's area. An internal combustion engine frequently lies within the engine compartment in front of a tunnel formed on the underside of the watercraft hull. The internal combustion engine powers a jet pump unit located within the tunnel. An impeller shaft commonly extends between the engine and the jet pump unit for this purpose.
One end of the impeller shaft is coupled to an output shaft of the engine while the other end extends into the jet pump unit and drives an impeller. The orientation of the impeller shaft within the hull therefore is fixed by the mounted positions of the engine and the jet pump unit within the hull.
A bearing assembly, which is affixed to a bulkhead, supports the impeller shaft between the engine and the jet pump unit in many personal watercraft. The position and orientation of the bearing assembly, and thus the bulkhead, within the hull thus becomes important in order to properly support the impeller shaft. Misalignment occurring between the bearing assembly and the impeller shaft causes increased wear between these components and often produces stress within other components of the drive train, such as in the coupling between the impeller shaft and the engine output shaft.
For this purpose, the bulkhead often is bonded into the hull using a jig. The jig is placed in the hull, usually flush against the transom. In this position, the front end of the jig establishes the position and the orientation of the bulkhead. After the bulkhead is attached to the lower hull section, the jig is removed and the upper deck of the hull is attached.
Use of a jig to locate the position and orientation of the bulkhead within the hull poses several drawbacks. Position and orientation errors of the transom are translated to the bulkhead using this manufacturing technique. Manufacturing errors caused by incorrect positioning of the jig within the hull also attribute to the occasional mispositioning of the bulkhead. And such positioning errors often translate into increased friction and stress between the impeller shaft and the bearing assembly attached to the bulkhead.